1. Field of the Invention
The present invention generally relates to a steer by wire system. More specifically, the invention relates to an end of travel and method for a steer by wire system.
2. Description of Related Art
In a conventional steering system, the steering wheel is mechanically connected to the steering shaft. When the mechanical end of travel of the vehicle wheels or the steering gear is reached, (an “end of travel” condition), the steering wheel cannot be rotated any further due to high mechanical resistance. However, in normal operation a steer by wire system has no mechanical coupling to the steering gear. The lack of feedback torque for the driver at the end of travel condition is unfamiliar and uncomfortable for the driver. In addition, extensive use of the steering system in an end of travel condition such as the limit of steering gear travel or an against curb condition can cause additional wear to the vehicle and may lead to early replacement of various system components.
To simulate the feel of a mechanically connected steering system, many steer by wire systems have incorporated an electric motor coupled to the steering wheel. The electric motor is designed to simulate the resistance patterns of a conventional mechanically connected steering system. When the end of travel conditions are encountered in a steer by wire system, the driver can continue turning the steering wheel contrary to a conventional mechanically connected steering system. To simulate an end of travel condition of a conventional steering system, some steer by wire systems have incorporated a brake directly coupled to the steering shaft. The brake can be engaged to prevent the driver from turning the steering wheel any further. Unfortunately, these brakes consume a significant amount of power and occupy a significant amount of space when attached directly to the steering shaft.
In view of the above, it is apparent that there exists a need for an improved power module for automotive switching applications.